The photolysis of pentafluoroacetone

The photolysis of pentafluoroacetone has been investigated in the 3130 Å region, from room temperature to 360°C. The Φ CO varies from 0.7 to 0.9 over this range, and the decomposition is represented by CF 2 HCOCF 3 → CF 2 H + CO + CF 3 . The disproportionation/combination ratio for CF 3 and CF 2 H (→ CF 3 H + CF 2 ) radicals is found to be 0.09. Arrhenius parameters for hydrogen atom abstraction from the ketone are log 10 A = 12.7 (units are mole −1 cc sec −1 ) and E = 14.3 kcal mole −1 for CF 2 H, and log 10 A = 12.1 and E = 11.8, for CF 3 radicals. At low pressures HF elimination reactions are observed from the vibrationally excited fluoroethanes, C 2 F 5 H* and C 2 F 4 H 2 *, formed in the system. A rough estimate of the activation energy for the process C 2 F 5 H → C 2 F 4 + HF of 60–65 kcal mole −1 is made.